Sensor Receptor Physiology

Question 1

Describe an adequate stimulus

Answer 1

It is when each type of receptor is specialised to respond to one type of Stimulus

Question 2

Name different types of sensory receptors

Answer 2

• photoreceptors
• mechanoreceptors
• thermoreceptors
• osmoreceptors
• chemoreceptors
• nociceptors

Question 3

What are compound sensations?

Answer 3

It is the perception that arises from the integration of several activated primary sensory inputs

.e.g perceptions of wetness comes from touch, pressure and thermoreceptor input. There is no such thing as a wetness receptor

Question 4

What do osmoreceptors detect?

Answer 4

They detect stretch due to water volumes - osmotically

Question 5

What stimulates chemoreceptors?

Answer 5

• oxygen
• pH
• organic molecules .e.g glucose

Question 6

What stimulates mechanoreceptors?

Answer 6

• pressure (baroreceptors)
• cell stretch (osmoreceptors)
• vibration
• acceleration
• sound

Question 7

What stimulates photoreceptors?

Answer 7

Photons of light

Question 8

What stimulates thermoreceptors

Answer 8

Varying degrees of heat

Question 9

How is receptor information conveyed to the CNS?

Answer 9

Via afferent neurons

Question 10

Describe transduction

Answer 10

The energy conversion of a sensory stimulus into an action potential

Question 11

What is the importance for the processing of sensory input by the brain stem?

Answer 11

• cortical arousal

- consciousness (allows us to be aware of the world around us)

Question 12

What generates a receptor potential?

Answer 12

The stimulation of the receptor will change the membrane permeability by opening ion channels for sodium to move in (electrochemical gradient) and this will depolarise the cell

Question 13

What is a disadvantage of a receptor potential?

Answer 13

As the potential moves further away from the source the weaker the signal gets

Question 14

What does the amplitude and variation of a receptor/grade potential depend on?

Answer 14

• The strength and rate of stimulus

- The removal of the stimulus

Question 15

Why must a receptor potential be converted into a action potential?

Answer 15

So that the transmission can be extended further along the afferent fibre

Question 16

How is stimulus intensity distinguished?

Answer 16

• by the number of action potentials generated in the afferent neuron
• number of receptors activated within the area (size of the are stimulated)

Question 17

Complete sentence: the intensity of a stimulus is reflected by….

Answer 17

The magnitude of the receptor potential

Question 18

Describe the phenomenon - adaptation

Answer 18

Some receptors can get rid of their depolarisation even if there is a sustained stimulus strength

Question 19

Name two receptors based in their speed of adaptation

Answer 19

• tonic receptors

- physic receptors

Question 20

What is the trigger zone ?

Answer 20

It is where the receptor potential is integrated

Question 21

Describe the relationship between frequency of action potentials and stimulus intensity

Answer 21

The frequency of action potentials are proportional to stimulus intensity

Question 22

True/False : the duration of a series of action potentials is proportional to stimulus duration?

Answer 22

True

Question 23

Why don’t tonic receptors adapt?

Answer 23

They need to generate action potentials continuously to relay relevant information to the CNS

Question 24

Name examples of tonic receptors

Answer 24

• muscle stretch receptors that monitor muscle length

- joint proprioceptors that measure stretch within joint

Question 25

In what situations are phasing receptors important?

Answer 25

When it is important to change the intensity of the stimulus rather relay information that it is switched on

Question 26

Which receptors are rapidly adapting receptors ?

Answer 26

Physic receptors

Question 27

What is the "off response" regrading phasic receptors

Answer 27

When a stimulus is removed the receptor will slightly depolarise

Question 28

Where is the somatosensory cortex?

Answer 28

Post gyrus

Question 29

When the afferent information reaches the spinal cord, where does it go?

Answer 29

Either to the: - reflex arc - up to the brain for further processing

Question 30

What do labelled lines do?

Answer 30

They stop information from getting muddled until it reaches the somatosensory cortex

Question 31

What are labelled lines?

Answer 31

They are discrete chains of neurons that convey conscious somatic sensation in a particular sequence. They do this to create more accurate processing of sensory information

Question 32

Describe the pathway from the afferent neuron to the somatosensory cortex

Answer 32

First order sensory neuron synapses on a second order sensory neuron (in the spinal cord/medulla) This then synapses with a third sensory neuron (in the thalamus) This will then reach the somatosensory cortex

Question 33

What is a receptive field?

Answer 33

It is a region on the skin surface where a somatosensory neuron will respond to a stimulus

Question 34

What affects somatosensory acuity

Answer 34

>The size of the receptive field -the smaller the receptive field, the greater the acuity >lateral inhibition

Question 35

Can subtle differences in a large receptive field be detected?

Answer 35

No as this decreases somatosensory acuity

Question 36

Where in the body will you find many receptive fields that are small?

Answer 36

In the fingertips and the lips

Question 37

What is innervation density?

Answer 37

It is when there is more cortical space allocated for areas with smaller receptive fields

Question 38

What is lateral inhibition?

Answer 38

It is a mechanism that tries to figure out where the exact receptor field is

Question 39

What do inhibitory neurons do?

Answer 39

They sit laterally to the receptive field stimulated and block off transmission so that information can be contrasted easily. It helps distinguish between wanted and unwanted information so that the main stimulus can be precisely localised

Question 40

What areas in the body have the most lateral inhibition and why,

Answer 40

Areas of touch and visions to bring about more accurate localisation